Under P.L. 90-602, "The Radiation Control for Health and Safety Act of 1968", there is a need for suitable portable equipment for making measurements connected with the testing of diagnostic X-ray equipment for compliance with this Act, for example, measurements to test the ability of the AC power supply to meet the equipment's minimum requirements, as specified by the manufacturer. Specifically, there is a need to measure accurately the true-RMS voltage, frequency, and percent regulation of the AC power supply, and to obtain clear displays of this information. Previously employed measuring equipment suffered from lack of adequate resolution and accuracy, limited voltage range, lack of means to compute percent regulation, and degradation of voltage accuracy with variation of the input frequency. Thus, there is a need for portable measuring equipment which can record small voltage changes, for example, as small as 0.1 volt, which can accurately compute percent regulation, and which can measure inputs at least from about 16 Hz to about 1.6 kHz.
A preliminary search of the prior art revealed the following prior U.S. Pat. Nos. of interest:
Wright, 3,205,347,
Platzer et al, 3,423,578,
Plante, 3,657,528,
Engel, 3,743,949,
Allen, 3,840,813,
Silberberg, 4,006,413,
Funk, 4,080,568,
Buhlmann, 4,125,895.